1. Field of the Invention
This invention concerns a flow control device for therapeutic solutions in a infusion line of a type including a valve with a seal for the infusion line and a circuit for controlling the position of the seal in order to control the flow of therapeutic solution through the valve.
2. Description of Prior Art
Treatment for a certain number of illnesses, such as diabetes, cancer, etc., using chemotherapy requires the practice of infusion on a continuous or intermittent basis, for the purpose of administering one or more therapeutic solutions to the patient.
Infusion systems may be either fixed, generally in a hospital setting, where the flow of therapeutic solution is gravitational, for instance from a plastic bag suspended above the patient's bed, or portable, using a pump carried by the patient for automatic injection of the therapeutic solution into the patient's body. Whichever of these infusion systems is used, it is sometimes necessary to improve the efficiency and safety of the system by adding a flow control device.
Earlier techniques relied on various means for controlling the flow of therapeutic solution. Thus, U.S. Pat. No. 4,623,331 describes a infusion system using a suspended bag in which an alarm is set off when an incorrect number of drops is delivered by the infusion line. This is not truly a flow control device, but rather a simple security device.
U.S. Pat. No. 4,616,801 describes a system using an eccentric roller to compress the infusion line by electrically controlled rotation. The degree of compression modulates the flow. Obviously, the precision of such a system can only be approximate.
U.S. Pat. No. 4,038,981 describes a infusion line with an electromagnetic ball valve for regulating the number of drops over time, setting a minimum and maximum number of drops. The sole purpose of the electromagnetic control of the valve is to raise or lower the ball, i.e., open or close the valve. This system clearly does not provide constant flow control of the therapeutic solution but only counts the number of drops supplied, without any possibility of controlling the volume of each drop.